Among some 3D printing methods, generally, a 3D printing method for fusing and depositing thermoplastic resin (which is commonly called FDM (Fused Deposition Method)) is carried out by fusing the thermoplastic resin to mold a long filament having a given diameter (about 1.75 mm or 3 mm), winding the filament on a spool, mounting the spool on a device, passing the filament fed from the spool through a nozzle on which a heater is mounted to allow the filament to be fused, and continuously depositing the liquid resin discharged from the nozzle, thereby printing a 3D product.
For example, in case where an expected amount of filament to be consumed (which is recognized through a program setting printing conditions) for a product to be newly made is over 100 g in the state where the amount of filament on a spool in use is 100 g, if printing starts, without any exchange of the spool in use, the consumption of the filament wound on the spool in use is observed. Just before the amount of filament on the spool in use is completely consumed, the spool in use has to be exchanged into a separate spool on which a new filament is wound.
Further, it is hard to expect whether the time at which the remaining amount of filament on the spool in use is consumed is night, dawn, weekend, etc., and accordingly, if it is desired to exchange the spool in use into the separate spool during the printing after the remaining amount of filament on the spool in use is consumed, a substantially large amount of manpower is needed. As a result, generally, the printing starts after the exchanging.
For these reasons, users who use the 3D printers through the FDM have a plurality of spools on which specific amounts of filaments are remaining, and if it is desired to make appropriate printing products for the spools, they try to exchange the spools into the spools in use and to consume the remaining amounts of filaments on the spools. Actually, it is very difficult to handle the remaining amounts of filaments on the spool.
So as to solve the above-mentioned problems, a filament welding machine has been proposed to weldedly connect two filaments to each other, but to do this, the remaining filament is unwound from the spool in use, connected to a filament of a new spool, and is wound on a spare space on the new spool, which still makes it difficult to continuously connect and use the spools.